The $\Lambda_b\to\Lambda^\ast(1520)(\to N\!\bar{K})\ell^+\ell^-$ decay at low-recoil in HQET

Understand

In this paper we discuss the Standard Model and new physics sensitivity of the $\Lambda_b\to\Lambda^\ast(1520)(\to N\!\bar{K})\ell^+\ell^-$ decay at low-recoil, where $\ell^\pm$ are massive leptons and $N\!\bar{K}=\{pK^-, n\bar{K}^0 \}$.

• We provide a full angular distribution with a set of operators that includes the Standard Model operators and their chirality flipped counterparts, and new scalar and pseudo-scalar operators.
• The resulting angular distribution allows us to construct observables that we study in the Standard Model and in model-independent new physics scenarios.
• To reduce the hadronic effects emanating from the $\Lambda_b\to\Lambda^\ast(1520)$ transition form factors, we exploit the Heavy Quark Effective theory framework valid at low $\Lambda^\ast(1520)$ recoil, \emph{i.e.,} large dilepton invariant mass squared $q^2\sim \mathcal{O}(m_b^2)$.